WASHINGTON — President Biden on Sunday cited the Buffalo shootings in calling for national unity as a remedy for “the hate that remains a stain on the soul of America,” while New York’s governor and the city’s mayor appealed for forceful action from Washington after the latest mass shooting had caused a community to grieve.

Mr. Biden used his remarks at a Capitol ceremony honoring law enforcement officers who died in the line of duty in 2021 to decry what he said his Justice Department has labeled as “a hate crime, a racially motivated act of white supremacy and violent extremism.”

Authorities say that a white gunman in military gear attacked shoppers and workers at a supermarket in Buffalo, New York, on Saturday, killing 10 people, including a retired Buffalo police officer, and wounding three others. Most of the victims were Black. Law enforcement officials said Sunday that the 18-year-old gunman had researched the local demographics while looking for places with a high concentration of Black residents.

“A lone gunman, armed with weapons of war and hate-filled soul, shot and killed 10 innocent people in cold blood at a grocery store on Saturday afternoon,” Mr. Biden said at the 41st annual National Peace Officers’ Memorial Service.

“We must all work together to address the hate that remains a stain on the soul of America. Our hearts are heavy once again, but the resolve must never, ever waver. No one understands this more than the people sitting in front of me,” the president said.

Mr. Biden did not address calls by Governor Hochul and Buffalo’s mayor, Byron Brown, for strong federal action in the aftermath of the latest act of mass violence in the United States. His brief remarks did not mention gun control efforts that have stalled in Washington.

“We’ve seen many of these mass shootings around the country year in and year out, month in and month out. And it’s always the same refrain. People send their thoughts and their prayers. Lawmakers in Washington say that there’s something that must be done,” Mr. Brown told NBC’s “Meet the Press.”

“And then there are some on one side of the aisle that block anything from being done. It seems like there are those that believe owning a gun is more precious than the sanctity of human life. So I think people all across this country have to rise up. They have to speak more loudly and more clearly that there must be gun control in this country. This is a uniquely American phenomenon. These mass shootings don’t happen in other countries across the world,” he said.

Mr. Brown said he would like to see “sensible gun control.”

The House speaker, Nancy Pelosi, said tighter gun measures are “a huge priority” for Democrats and the White House. She bemoaned the 60-vote threshold needed in the 50-50 Senate that has made it so difficult to advance such legislation, but pledged on CNN’s “State of the Union” that “we are not going away until the job is done.”

Ms. Hochul said that most of what she described as “the illegal guns” being used on the streets of her state’s cities are coming from other states. “We need a national response,” she told NBC.

“We need other states to step up. We need the federal government on our side.”